Method of inhibiting hydrochloric acid against corrosiveness to ferrous metals



T. B. M CULLOCH METHOD OF INHIBITING HYDROCHLORIC ACID AGAINST GORROSIVENESS TO FERROUS METALS Filed April 12, 1941 V w fiai mgca 1 Exam Patented July 10, 1945 a "'ffzsaezsr e 'METHOD OF INHIBITING BYDBOOHLOBIO ACID'AGAINST COBIIOSIVENESS (1'0 FEB.- BOUS METALS 7 I Thomas B. MoCnlloch, Baytown, 'l'ex., mignor' to Standard Oil Development Company, a cor- I 1 p pontion of Delaware Application April 12, 1941, Serial No. 388,256

. I 11 Claims. (Cl. 251-148) This invention relates to a composition of matsludges derived from sulfuric acid treatment of ter and a method or producing same. I More parpetroleum fractions. Y ticularly, it is concerned with improved aqueous It has now beenfound that aqueous hydrohydrochloric acid solutions whose corrosivenesschloric acid solutions can be inhibited again! to metals, especially steel, has been greatly abated corrosiveness to metals, particularly steel, by con by contacting the acid with crude phenolic matetacting the acid with crude troleum henols. rials of petroleum origin which for ease or dis- The nature and quantity'brinmbiting agent excussion will hereinafter be referred to as .crude tracted from the crude petroleum phenols by the petroleum phenolic materials. hydrochloric acid is not known, but the quantity The crude petroleum phenolic materials used in m is believed to be very smallusually less than 0.1% the present invention are obtained by extracting of the extracting acid and probably less than 1% crude petroleum oils, and distillates thereof, with I of the crude petroleum phenols. Nevertheless, an alkali, suitably an aqueous solution of the it has been found that, with good agitation andhydroxide or carbonate of an alkali metal or contact, 1 pound of crude petroleum phenols will ammonium. The crude petroleum phenolic soaps 15 properly inhibit approximatelyilfl pounds of 38%, thus obtained may be used directly in the process 1 strength hydrochloric 'acid solution or 76 pounds of this invention, or the crude phenols may be of 15% strength hydrochloric acidsolutionr first liberated by treatment with a suitable acid, In extracting the inhibitor agent from the crude such as CO: or a mineral acid. These materials petroleum phenols, it is preferable to employ conare preferably used in the present invention in centrated, rather than dilute, aque us hy r substantially the same crude state in which they chloric acid solution since the former is a better a are separated from the petroleum oil, with no solvent or extraction agent for the inhibitor and further purification than the separation of excess less quantity oi acid has to be handled durins alkali and other insoluble materials. Puriflcathe extraction operation. The concentrated acid tion of these phenolic materials by distillation, or can be diluted after inhibition 'to any desired y repeated extraction with alkali followed by 'weaker strength without. destroying or degrading reacidiflcation, for example, generally render the effectiveness of the inhibitor cont n therethem less effective for use in the present invenin. After the inhibitor has been extracted from i tion. Apreierred type of crude petroleum phenols the crude petroleum phenols, the latter may be is the oily material secured upon partially orcompletely acidiiyins.with carbon dioxide orv mineral inhibiting oxidation and gum formation in acid, the soaps obtained by washing petroleum cracked gasolines. No difficulty 1 encwmflied dlstillates, especially cracked distillates boiling in separating the crude petroleum phenols from the the range between about 250 F. and 750 F., with hydrochloric acid since they are only very $118 strong aqueous alkaline solutions, particularly 30 soluble in this reagent or in water. to 50 Baum gravity strength alkali metal hy-- The drawing is a diagrammatic sketch in par- 1 droxide solutions. Methods of obtaining these tiaisectlonal elevation of equipment suitable for V crude petroleum phenols are described in U. S. carrying out the process or this invention; It 2 Patent 2,213,596. m h-ates on modification of the process for It is known in the art that aqueous-hydro 4o inhibiting hydrochloric acid against corroslvechloric acid solutions can be inhibited against mess to metals, particularly steel, by contacting corrosiveness to metal surfaces in a manner that the acid n d petroleum phenols. In this does not destroy or degrade the usefulness of the ification, crude petro e phenols. are introacid forsuch purposes as acidizing oil, gas or t o drowater wells and dissolving water;,insolublesalt.dc-' duced through line l into fresh 5 r m hy purified andlused for other purposes such as for mm the mcfifhsakexchangeequinf mm'TsmFbf fact, inhibiting the corroi si'veness or the acid to metals enhances its value It is known also that hydrochloric acid solutions are rendered substantially non-corrosive to metals by adding thereto small 5 amounts of such substances as arsenic acid, a;-

se ioxidwJurfurg], the furans, nitrogen flallilldinei .qi ll oline, etc.) i organic q id 55 phenols phase iswithdrawn from settler 5 through for these. uses.

sulfur compounds (mercaptans, etc), an

chloric acid solution, preferably of about 38 weight per cent strength concentration, being charged through line 2. This mixture is then passed througha mixing pump 3 (or equivalent means) where thorough mixing and good contact between the acid and phenols is eilected before the mixture is discharged through line 4 to set-; tier I. In settler i, the acid-phenols mixture separates into two phases. The crude petroleum I i i i i i drawn through line II.

In some cases, it may be desirable to discard from the system, through line 'I all of the crude petroleum phenols withdrawn from settler I by means of line 8, However, it is generally preferable to discard only a portion of these phenols, the balance being recycled through line 8 to line I. Fresh make-up crude petroleum phenols are introduced into the system by means of line 9 which is in communication with line I.

The inhibited strong hydrochloric acid solution in line I! may be passed directly to storage through line H; however, in some cases, it may for thorough mixing before being sent to storage. Since diluting the concentrated acid with water results in a considerable temperature rise (approximately 50 F. for equal volumes of acid and water), it is preferable to precool the dilution waterby means of cooler II in line I3 ahead'of the point of introduction of the acid. If desired. the acid may also be cooled either before or after dilution.

The conditions of temperature, strength of extraction acid, and volume ratio of extraction acid to fresh crude petroleum phenols may be varied over a considerable range and still secure satisfactory inhibition of the acid. For example, the extraction temperature may range between 40' and 100 1"., but the preferred range is between 80' and 80 F. The strength of the hydrochloric acid solution employed to extract the inhibitor from the crude petroleum phenols may vary between about 20% and 43% BC] by weight; however, the preferred strength is in the range between 34% and-38% HCl. The volume ratio of extraction acid to fresh crude petroleum phenols Although it is not essential that part of the extracted crude petroleum phenols, withdrawn from settler I through line 8, be recycled through line 8, this procedure is preferred, particularly.

,2 g assess line s and the hydrochloric acid phase is with- REitRrNCiE system, through line 1, an amount of extracted crude petroleum phenols equivalent to the amount of fresh crude petroleum phenols charged to the system through line 9.

Although this invention has been described with reference to a specific embodiment of a process for contacting the hydrochloric acid with crude petroleum phenols, it is to be understood that any method and means of securing intimate contact between the acid and the crude petroleum phenols may be employed with satisfactory resuits. For example, the principles of countercurrent contact may be employed, using either a single tower or a multi-stase set-up.

A modification of the afore-described or preferred method of inhibiting hydrochloric acid against corrosiveness to metals, especially steel,

consists of contacting the acid to be inhibited directly with crude petroleum phenolic soaps which have been secured by washing petroleum distillates, particularly cracked distillates, boiling in the range between about 250 F. .and 750 F. with strong aqueous alkaline solutions, especially to 50 Baum gravity strength caustic solutions. In this modified process, the contacting of 'the acid to be inhibited with the crude Hence, the process may be considered, as differing from the one previously described only in respect to the omission of a preliminary step in which the crude petroleum phenols are liberated and freed of undesirable salts before coming in contact with the hydrochloric acid to be inhibited. Although this modified process will accomplish the desired result, it is less attractive for commercial operation than is the preferred process (previously described) for three reasons: (1) the large quantity of heat liberated upon reaction of the concentrated hydrochloric acid with the soaps would necessitate the use of elaborate and expensive cooling facilities 'for controlling the temperature of the reaction mixture; (2) a loss in acid strength would result from the utilization of H01 to neutralize and acidity the soaps; (3) the expensiveness of hydrochloric acid in comparison with that of sulfuric acid or carbon dioxide makes its use as a reagent for neutralizing and acidifying the crude petroleum when employing high ratios of extraction acid to fresh crude petroleum phenols. By recycling part of the crude petroleum phenols, instead of employing a once-through operation, better contact between the acid and the phenols is secured, thereby insuring more eifective inhibition of the u acid. Furthermore, such a procedure is conducive to a more stable operation and facilitates better separation of dispersed crude petroleum phenols from the acid phase in the settler. when employing the recycle operation, the volume ratio of acid to the total (fresh plus recycled) crude Petroleum phenols charged to the mixing pump 3 Y may vary between the limits or about 50:1 to

05:1: however, the preferred range is between the limits of 10:1 to 2:1. In order to maintain equilibrium conditions in a recycle operation of ture which must be provided in order to control the reaction temperature and for slightly different ratios of hydrochloric acid to fr'esh crude petroleum phenolic soaps. The quantity of crude petroleum phenolic soaps required to properly inhibit the acid varies considerably with the qualit! and type ofsoaps employed. However, it is usually possible to satisfactorily inhibit about 8 to 12 volumes of concentrated hydrochloric acid or 12 to 18 volumes of dilute hydrochloric acid by intimately contacting the acid with one volume of a well-settled crude petroleum phenolic I soap, especially where the soap is derived from the treatment ofcracked petroleum distillates boiling in the range-between about 250' and 750 this nature. it is necessary to withdraw from the rs Ewith. a. 40' to aum 6 gravity strength causaseomsc 3" scribed in the preceding paragraph, The results are also tabulated in Table I below:

tic solution. The undissolved crude petroleum phenols, which are liberated from the soaps upon contacting the latter with the hydrochloric acid, may be settled and separated from the acidin the manner previously described. Likewise, a

portion of the undissolved crude petroleum phenols may be recycled and mixed with the incoming charge of fresh crude petroleum phenolic soaps. The ratio of recycled crude petroleum phenols to fresh crude petroleum phenolic soaps preferably varies between about 1:1 to 10:1.

When starting with crude petroleum phenolic soaps as a source of inhibitor for hydrochloric acid, the preferable procedure is to first settle out and separate as much of the caustic (or alkaline reagent) as possible; then dilute the soap solution with about an equal volume of water. This dilution usually causes separation of some neutral oils which are preferably removed from contact with the dilute soap solution before the latter is acidified with a .suflicient amount of dilute sulfuric acid (of approximately 30% strength) or carbon dioxide to partially or completely liberate (as desired) the crude petroleum phenols contained therein. Salt may be added to the aqueous solution to increase its density and thereby facilitate a more rapid separation of the oily, liberated crude petroleum phenols from the aqueous phase. After separating them from contact with the aqueous solution liberated therefrom, the crude petroleum phenols may be contacted directly with the hydrochloric acid to be inhibited in accordance with the preferred method.

The following examples are presented for purpose of illustrating the feasibility of inhibiting hydrochloric acid against corrosiveness to steel by contacting the acid with crude petroleum phenols. These examples are not to be construed as limiting the scope of the invention in any manner whatsoever.

100 grams of a 38% strength hydrochloric acid solution in water were mixed with 10 grains of crude petroleum phenols derived from a mixture of cracked and straight-run distillates boiling in the range between 250 F. and 750 F., and the mixture was stirred for 5 minutes. After settling and separating the crude petroleum phenols phase from the acid phase, the latter was tested for its corrosiveness to steel by immersing in it for 24 hours a weighed strip of steel of known surface area. This steel strip was then removed, carefully washed and dried, and then reweighed to determine the loss of metal due to corrosion.

By a process of simple calculation, the corrosion units were converted from weight of metal lost per unit surface area per day to inches of penetration into the metal per year," since the latter units are more comprehensible and more convenient for use than are the former. The results obtained in this experiment are tabulated in Table I below. As a basis for comparison, the corrosiveness of uninhibited 38% strength hydrochloric acid solution to steel, tested under the same conditions, is also listed.

For purpose of comparison, asecond 100-gram batch of 38% strength hydrochloric acid was contacted for 5 minutes with grams of crude petroleum phenols derived from only cracked distillates boiling in the range between 250 F. and 750 F. After settling and separating the phenol phase from the acid phase, the latter was tested i=1 its corrosiveness to steel by the method dewe r Penetration o! corrosion Corrosive agent into steel, inches per year 38 strength HCl solution uninhibited 7. 26' 38 a strength HCl solution inhibited by contacting with crude petroleum phenols derived from mixture of cracked and straight-run distillates 0. 0000 38% strength HCl solution inhibited by contacting with crude petroleum phenols derived from only cracked distillates 0. i186 Emu: 2

The fact that the acid inhibiting power displayed by the crude petroleum phenols is not an inherent property of phenolic type compounds is demonstrated in this experiment.

A IO-gram sample of commercial Tricresol and a i-gram sample of commercial phenol (carbolic acid) were contacted for 5 minutes with separate 100-gram batches of 38% strength hydrochloric acid solution. The commercial phenol was completely dissolved by the acid but the Tricresol was not; hence, the latter material had to be separated from its corresponding batch of acid before both samples of inhibited acid could be tested for their corrosiveness to steel in accordance with the method described under Example 1. Both of these inhibited acids were very corrosive to steel, as will be noted from the data in Table 11.

Hence, Tricresol and carbolic acid must be con-.

sidered as very poor inhibitors against corrosive- This experiment illustrates the effect which temperature has upon the rate that steel is corroded by hydrochloric acid, both weak and strong solutions, which have and which have not been inhibited in accordance with this invention.

100 parts by weight of 38% strength aqueous hydrochloric acid were contacted with 10 parts by weight of crude petroleum phenols for 5 minutes at F. The mixture was then allowed to settle; after which, the acid phase was separated from the phenol phase. Samples of this inhibitedacid and also samples of uninhibited 38% strength aqueous hydrochloric acid were tested for their corrosiveness to steel at temperatures of 75, and F. in accordance with the method described under Example 1. Similarly, samples of both the inhibited and the uninhibited 38% strength aqueous hydrochloric acid solutions were diluted to 15% strength solution and each was then tested in a like manner for its corrosiveness to steel at temperatures of 75, 135,

and F. The results are listed in Table mbelowa Table III Penetration of corrosion into SM Temperature of steel, inches per year gdrmlom contact bo- $.33? tween acid and 8 mm 5 mo, 1. Uninhibitsd mlggsa 88 7 26 0.09 88 25- U 0. 8861 88 no 9. 46 18. 79 88 194- 7 101. 8 15 76 0. mo 0. (B8 16 135 4. 83 0. 1812 16 13. 16 1- 09 15 21. 12 14. 62

It will be noted that the inhibited 88% strensth acid corrodes steel rapidly at temperatures above about 100 F., but that the inhibited 15% strength acid may be employed at temperatures above 155 -F. without experiencing excessive corrosion on steel. In acidizing oil wells, it is customary to employ 15% strength'hydrochloric acid at elevated temperatures; hence, the properties of the 15% strength acid are favorable for this usage.

Exsnrui A l07 -gram batch of crude petroleum phenols was shaken vigorously for 5 minutes with three separate and successive lO'lO-gram batches of fresh 38% strength hydrochloric acid solution. In each case, the undissolved portion of the phenols was separated from the acid and the inhibited acid was divided into two parts. One

I portion of each batch of acid thus inhibitedwas tested per se for its corrdsiveness to steel strips in accordance with the method described under Example 11 The second portion of each separate batch oi inhibited acid'was first diluted to a 15% strength solution and then tested for its corrosiveness to steel by this same method. The results obtained in this experiment are tabulated below:

It will be noted from these data that the third batch of acid contacted with the petroleum phenols showed little or no corrosion inhibition properties when employed in the undiluted state but, when diluted to a 15% strength solution, satisfactory inhibition was manifested. The nature of this phenomenon is not understood. but it is an important feature since most of the uses for inhibited acid employ theweak, rather than the strong. solution. The data also indicate that, had counter-current contact between the acid and the crude petroleum 1 phenols been employed, one pound of the crude petroleum phenols would have satisfactorily inhibited approximately 20 pounds 2 gallons) of 38% strength hydrochloric acid or approximately 76 pounds (8 gallons) of 15% strength hydrochloric acid.

- p troleum phenols in the manner described in this applicatiomespeciallythe dilute solutions, are particularly well adapted (or use in acidising oil. gas and water wells to increase their rate oi iitr tumor.

. assess D 'hibited acid is in the dissolution and removal 01' water-insoluble salt deposits from heat exchange equipment. Steam boilers, heat exchangers, etc..

handling hard waters gradually lose their heat transfer efliciencies while in operation due to deposition of water-insoluble salts on their heat transfer surfaces. These water-insoluble salt deposits are most conveniently removed by circulating hydrochloric acid through the equipment. In order to avoid excessive damage to the equipment. it is desirable to employ an acid that has been inhibited against corrosiveness to steel. Hydrochloric acid inhibited by contacting same with crude petroleum phenols is particularly well adapted for this purpose.

It is permissible and desirable in some cases to incorporate with the inhibited hydrochloric acid (or this invention) an acid intensifying agent such as the fluorides of sodium. potassium, ammonium, hydrogen, lithium, aluminum, and tin. Similarly, surface activating agents may be incorporated with the inhibited acid. Some particularly good surface activating agents are: the amino alcohols, the sulfonated alcohols, the alkylated aryl sulfonates and other compounds of similar composition and characteristics.

The nature and objects of the present invention having thus been described what is claimed as new and novel and what is desired to be protected by Letters Patent isi I l. A composition or matter comprising aqueous hydrochloric acid and an inhibitor 0! ferrous metal corrosion, said inhibitor being derived from crude phenols oi petroleum origin by extraction oi such phenols with hydrochloric acid.

2. A composition of matter comprising aqueous hydrochloric acid and not more than 0.1 per cent of an inhibitor of ferrous metal corrosion, said inhibitor being derived from crude phenols of petroleum origin by extraction of such phenols with hydrochloric acid.

3. The method of inhibiting hydrochloric acid against corrosiveness to ferrous metals which comprises contacting said acid with crude phenols of petroleum origin, settling the mixture, and separating the inhibited acid from the undissolved material.

4. The method of inhibiting strong aqueous hydrochloric acid against corrosiveness to ferhydrochloric acid against corrosiveness to, fer-' rous metals which comprises contacting a 84 to 38 per cent strength hydrochloric acid with crude phenols of petroleum origin in the ratio of 100 volumes of acid to between 6 and 8 volumes of crude phenols, settling the mixture, and separating the acid irom the undissolved crude phenols. 6. The method of producing a dilute hydrochloric acid solution which-is substantially noncorrosive to ferrous metals comprising contactin a 20 to 43 'per cent strength hydrochloric acid withcrude phenols of petroleum origin in the ratio of 100 volumes of acid to between 4 and 10 volumes of crude phenols, settling the mixture. separating the inhibited acid from the undissolved crude phenols, and diluting the acid with another important use for the in- It 'L 'l'ho method at producing adiiute hydro- Examine chlcric acid solution which is substantially noncorrosive to ferrous metals comprising contacting a 34 to 38 per cent strength hydrochloric acid with crude phenols of petroleum origin in the ratio of 100 volumes of acid to between 6 and 8 volumes of crude phenols, settling the mixture,

separating the inhibited acid from the undissolved,

crude phenols, and diluting the acid with water. 8. The method of inhibiting strong aqueous hydrochloric acid against corrosiveness to ferrous metals which comprises contacting a 20 to 43 per cent strength hydrochloric acid with a mixture of fresh and recycled crude phenols of petroleum origin in the proportion 01100 volumes of acid with 4 to 10 volumes 01' fresh crude phenols crude Iphenolates, settling the mixture, and septhe i'resh crude phenols being charged to the 'volumes of acid to between 8 and 13 volumes of arating the inhibited acid from the undissolved crude phenols liberated from the phenolates.

- 10. The method of producing a dilute hydrochloric acid solution which is substantially noncorrosive to ferrous metals comprising contacting a 20 to 43 per cent strength hydrochloric acid with crude phenolates of petroleum origin inIthe ratio of- 100 volumes oi acid to between 5 and 9 volumes of crude phenolates, settling the mixture, separating the acid from the undissolved crude phenols liberated from the phenolates, and diluting the acid with water. 11. The method of inhibiting strong aqueous hydrochloric acid against corrosiveness to ferrous metals which comprises contacting a 20 to 43 per cent strength hydrochloric acid with a mixture of fresh crude phenolates of petroleum origin and recycled crude phenols of petroleum origin in the proportion of 100 volumes of acid with 8 to 13 volumes or fresh crude phenolates and 4 to 10 volumes of recycled crude phenols,

settling the acid-phenols mixture, separating from the acid the undissolved crude phenols, recycling a portion of the undissolved crude phenols and mixing same with the fresh crude phenolates being'charged to the system.

, THOMAS B. MCCULLOCE 

